aboutsummaryrefslogtreecommitdiffstats
path: root/dyndhcpd.c
blob: 0cd009e994acb5effb0b21b3ca0bb3e741ea44be (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
/*
 * (C) 2013-2021 by Christian Hesse <mail@eworm.de>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 */

#include "dyndhcpd.h"

const static char optstring[] = "c:hi:l:p:u:vVw:";
const static struct option options_long[] = {
	/* name			has_arg			flag	val */
	{ "config",		required_argument,	NULL,	'c' },
	{ "help",		no_argument,		NULL,	'h' },
	{ "interface",		required_argument,	NULL,	'i' },
	{ "leases",		required_argument,	NULL,	'l' },
	{ "pidfile",		required_argument,	NULL,	'p' },
	{ "user",		required_argument,	NULL,	'u' },
	{ "verbose",		no_argument,		NULL,	'v' },
	{ "version",		no_argument,		NULL,	'V' },
	{ "write-config",	required_argument,	NULL,	'w' },
	{ 0, 0, 0, 0 }
};

/*** replace ***/
int replace(char ** config, size_t *length, const char ** tmp,
		const char * template, const char * value) {
	size_t templatelength = strlen(template);

	if (strncmp(template, *tmp, templatelength) == 0) {
		*config = realloc(*config, *length + strlen(value) + 1);
		*length += sprintf(*config + *length, value);
		*tmp += templatelength;
		return 1;
	}
	return 0;
}

/*** main ***/
int main(int argc, char ** argv) {
	int i, rc = EXIT_FAILURE, verbose = 0;
	const char * tmp;

	struct ifaddrs *ifaddr = NULL, *ifa;
	struct network network, dhcp, bootp;
	char * interface = NULL;

	char hostname[HOST_NAME_MAX];
	char * domainname;

	char * template = NULL;
	FILE * templatefile;
	const char * templatefilename = CONFIG_TEMPLATE;
	char * config = NULL;
	FILE * configfile;
	char * configfilename = NULL;
	size_t fsize, length = 0;

	char * pidfile = NULL, * leasesfile = NULL, * username = NULL;

	unsigned int version = 0, help = 0;

	/* get command line options */
	while ((i = getopt_long(argc, argv, optstring, options_long, NULL)) != -1)
		switch (i) {
			case 'c':
				templatefilename = optarg;
				if (strlen(templatefilename) == 0) {
					fprintf(stderr, "Requested different config file, but no name given.\n");
					return EXIT_FAILURE;
				}
				break;
			case 'h':
				help++;
				break;
			case 'i':
				interface = optarg;
				if (strlen(interface) == 0) {
					fprintf(stderr, "No interface given!\n");
					return EXIT_FAILURE;
				}
				break;
			case 'l':
				leasesfile = strdup(optarg);
				break;
			case 'p':
				pidfile = strdup(optarg);
				break;
			case 'u':
				username = optarg;
				break;
			case 'v':
				verbose++;
				break;
			case 'V':
				verbose++;
				version++;
				break;
			case 'w':
				configfilename = strdup(optarg);
				break;
		}

	if (verbose > 0)
		printf("%s: %s v%s (compiled: " __DATE__ ", " __TIME__ ")\n", argv[0], PROGNAME, VERSION);

	if (help > 0)
		fprintf(stderr, "usage: %s [-c config] [-h] -i INTERFACE [-v] [-V]\n", argv[0]);

	if (version > 0 || help > 0)
		return EXIT_SUCCESS;

	/* bail if we are not root */
	if (getuid() > 0) {
		fprintf(stderr, "You need to be root!\n");
		goto out;
	}

	/* check if dhcpd exists and is executable */
	if (access(DHCPDFILE, X_OK) == -1) {
		fprintf(stderr, "The dhcp daemon is not execatable!\n");
		goto out;
	}

	/* get the hostname */
	if (gethostname(hostname, HOST_NAME_MAX) == -1) {
		fprintf(stderr, "Failed to get the hostname.\n");
		goto out;
	}

	/* get the domainname and strip it from hostname */
	if ((domainname = strchr(hostname, '.')) != NULL) {
		*domainname = 0;
		domainname++;
	} else {
		fprintf(stderr, "Could not get domainname, using '" FALLBACKDOMAIN "'\n");
		domainname = FALLBACKDOMAIN;
	}

	/* give an error if we do not have an interface */
	if (interface == NULL) {
		fprintf(stderr, "No interface given!\n");
		return EXIT_FAILURE;
	}

	/* initialize ifaddr */
	if (getifaddrs(&ifaddr) == -1) {
		fprintf(stderr, "getifaddrs() failed.\n");
		return EXIT_FAILURE;
	}

	/* to find the correct interface */
	for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
		/* next iteration if requirements do not match */
		if (strcmp(interface, ifa->ifa_name) != 0)
			continue;
		if (ifa->ifa_addr == NULL)
			continue;
		if (ifa->ifa_addr->sa_family != AF_INET)
			continue;

		/* check if the device is up */
		if (!(ifa->ifa_flags & IFF_UP)) {
			fprintf(stderr, "Interface %s is down.\n", interface);
			goto out;
		}

		/* check if the device is connected / cable is plugged in
		 * do warn here, but do not fail */
		if (!(ifa->ifa_flags & IFF_RUNNING))
			fprintf(stderr, "Warning: Interface %s is not connected.\n", interface);

		/* get variables in place for address and netmask */
		memcpy(&network.address.i, &((struct sockaddr_in *)ifa->ifa_addr)->sin_addr, sizeof(struct in_addr));
		memcpy(&network.netmask.i, &((struct sockaddr_in *)ifa->ifa_netmask)->sin_addr, sizeof(struct in_addr));

		/* check if subnet has enough addresses */
		if ((network.netmask.i.s_addr & 0x0f000000) > 0) {
			fprintf(stderr, "We do not have addresses to serve, need a netmask with 28 bit minimum.\n");
			goto out;
		}

		/* calculate broadcast and netaddress */
		network.broadcast.i.s_addr = network.address.i.s_addr | ~network.netmask.i.s_addr;
		network.netaddress.i.s_addr = network.address.i.s_addr & network.netmask.i.s_addr;

		/* calculate for dhcp subnet */
		dhcp.netmask.i.s_addr = htonl(ntohl(network.netmask.i.s_addr) >> 1 | (1 << 31));
		dhcp.address.i.s_addr = network.address.i.s_addr ^ (dhcp.netmask.i.s_addr ^ network.netmask.i.s_addr);
		dhcp.broadcast.i.s_addr = dhcp.address.i.s_addr | ~dhcp.netmask.i.s_addr;
		dhcp.netaddress.i.s_addr = dhcp.address.i.s_addr & dhcp.netmask.i.s_addr;
		dhcp.minhost.i.s_addr = htonl(ntohl(dhcp.netaddress.i.s_addr) + 1);
		dhcp.maxhost.i.s_addr = htonl(ntohl(dhcp.broadcast.i.s_addr) - 1);

		/* calculate for pxe subnet */
		bootp.netmask.i.s_addr = htonl(ntohl(dhcp.netmask.i.s_addr) >> 1 | (1 << 31));
		bootp.address.i.s_addr = network.address.i.s_addr ^ (bootp.netmask.i.s_addr ^ dhcp.netmask.i.s_addr);
		bootp.broadcast.i.s_addr = bootp.address.i.s_addr | ~bootp.netmask.i.s_addr;
		bootp.netaddress.i.s_addr = bootp.address.i.s_addr & bootp.netmask.i.s_addr;
		bootp.minhost.i.s_addr = htonl(ntohl(bootp.netaddress.i.s_addr) + 1);
		bootp.maxhost.i.s_addr = htonl(ntohl(bootp.broadcast.i.s_addr) - 1);

		/* convert addresses from binary to text form */
		if (inet_ntop(AF_INET, &network.address.i, network.address.c, INET_ADDRSTRLEN) != NULL &&
				inet_ntop(AF_INET, &network.netmask.i, network.netmask.c, INET_ADDRSTRLEN) != NULL &&
				inet_ntop(AF_INET, &network.broadcast.i, network.broadcast.c, INET_ADDRSTRLEN) != NULL &&
				inet_ntop(AF_INET, &network.netaddress.i, network.netaddress.c, INET_ADDRSTRLEN) != NULL &&
				inet_ntop(AF_INET, &dhcp.minhost.i, dhcp.minhost.c, INET_ADDRSTRLEN) != NULL &&
				inet_ntop(AF_INET, &dhcp.maxhost.i, dhcp.maxhost.c, INET_ADDRSTRLEN) != NULL &&
				inet_ntop(AF_INET, &bootp.minhost.i, bootp.minhost.c, INET_ADDRSTRLEN) != NULL &&
				inet_ntop(AF_INET, &bootp.maxhost.i, bootp.maxhost.c, INET_ADDRSTRLEN) != NULL) {
			/* print information */
			if (verbose) {
				int pad = strlen(dhcp.minhost.c) > strlen(bootp.minhost.c) ?
					strlen(dhcp.minhost.c) : strlen(bootp.minhost.c);
				printf( "Interface:    %s\n"
					"Domain:       %s\n"
					"Host Address: %s\n"
					"Network:      %s\n"
					"Broadcast:    %s\n"
					"Netmask:      %s\n"
					"Hosts DHCP:   %-*s - %s\n"
					"Hosts BOOTP:  %-*s - %s\n",
						interface, domainname,
						network.address.c, network.netaddress.c,
						network.broadcast.c, network.netmask.c,
						pad, dhcp.minhost.c, dhcp.maxhost.c,
						pad, bootp.minhost.c, bootp.maxhost.c);
			}

			/* open the template for reading */
			if ((templatefile = fopen(templatefilename, "r")) != NULL) {
				/* seek to the and so we know the file size */
				fseek(templatefile, 0, SEEK_END);
				fsize = ftell(templatefile);
				fseek(templatefile, 0, SEEK_SET);

				/* allocate memory and read file */
				template = malloc(fsize + 1);
				if ((fread(template, fsize, 1, templatefile)) != 1) {
					fprintf(stderr, "Failed reading config template.\n");
					goto out;
				}
				fclose(templatefile);
				template[fsize] = 0;
			} else {
				fprintf(stderr, "Failed opening config template for reading.\n"
						"Using fallback to built in defaults, functionality is limited.\n");
				template = strdup(FALLBACKCONFIG);
			}

			/* replace strings with real values */
			for (tmp = template; *tmp;) {
				if (*tmp == '_') {
					if (replace(&config, &length, &tmp, "__INTERFACE__", interface) ||
						replace(&config, &length, &tmp, "__VERSION__", VERSION) ||
						replace(&config, &length, &tmp, "__HOSTNAME__", hostname) ||
						replace(&config, &length, &tmp, "__DOMAINNAME__", domainname) ||
						replace(&config, &length, &tmp, "__ADDRESS__", network.address.c) ||
						replace(&config, &length, &tmp, "__NETADDRESS__", network.netaddress.c) ||
						replace(&config, &length, &tmp, "__BROADCAST__", network.broadcast.c) ||
						replace(&config, &length, &tmp, "__NETMASK__", network.netmask.c) ||
						replace(&config, &length, &tmp, "__MINDHCP__", dhcp.minhost.c) ||
						replace(&config, &length, &tmp, "__MAXDHCP__", dhcp.maxhost.c) ||
						replace(&config, &length, &tmp, "__MINBOOTP__", bootp.minhost.c) ||
						replace(&config, &length, &tmp, "__MAXBOOTP__", bootp.maxhost.c)) {
						/* do nothing, work has been done */
					} else {
						config = realloc(config, length + 1);
						config[length++] = *tmp++;
					}
				} else {
					config = realloc(config, length + 1);
					config[length++] = *tmp++;
				}
			}
			config = realloc(config, length + 1);
			config[length++] = 0;

			/* get new filename and open file for writing */
			if (configfilename == NULL) {
				configfilename = malloc(strlen(CONFIG_OUTPUT) + strlen(interface) + 1);
				sprintf(configfilename, CONFIG_OUTPUT, interface);
			}

			/* try to open the config file for writing */
			if ((configfile = fopen(configfilename, "w")) == NULL) {
				fprintf(stderr, "Failed opening config file '%s' for writing.\n", configfilename);
				goto out;
			}

			/* actually write the final configuration to file and close it */
			fputs(config, configfile);
			fclose(configfile);

			/* get name for pidfile */
			if (pidfile == NULL) {
				pidfile = malloc(strlen(PIDFILE) + strlen(interface) + 1);
				sprintf(pidfile, PIDFILE, interface);
			}

			/* get name for leases file */
			if (leasesfile == NULL) {
				leasesfile = malloc(strlen(LEASESFILE) + strlen(interface) + 1);
				sprintf(leasesfile, LEASESFILE, interface);
			}

			/* check if leases file exists, create it if it does not */
			if (access(leasesfile, R_OK) == -1) {
				if (verbose)
					printf("Creating leases file '%s'.\n", leasesfile);
				fclose(fopen(leasesfile, "w"));
			}

			/* get use name */
			if (username == NULL)
				username = USER;

			/* execute dhcp daemon, replace the current process
			 * dyndhcpd is cleared from memory here and code below is not execuded if
			 * everything goes well */
			if (verbose > 1)
				printf("Running: dhcpd -f -q -4 -user %s -pf %s -lf %s -cf %s %s\n",
					username, pidfile, leasesfile, configfilename, interface);
			rc = execlp(DHCPDFILE, "dhcpd", "-f", "-q", "-4", "-user", username,
				"-pf", pidfile, "-lf", leasesfile, "-cf", configfilename, interface, NULL);

			fprintf(stderr, "The dhcp daemon failed to execute.\n");

			goto out;
		} else {
			/* failed to convert addresses from binary to string */
			fprintf(stderr, "Failed converting number to string\n");
			goto out;
		}
	}

	/* we did not find an interface to work with */
	fprintf(stderr, "Interface not found, link down or no address.\n");

out:
	/* free memory */
	if (leasesfile != NULL)
		free(leasesfile);
	if (pidfile != NULL)
		free(pidfile);
	if (configfilename != NULL)
		free(configfilename);
	if (config != NULL)
		free(config);
	if (template != NULL)
		free(template);
	if (ifaddr != NULL)
		freeifaddrs(ifaddr);

	return rc;
}

// vim: set syntax=c: